My long term objective is to understand the neural mechanisms underlying attention. Considerable progress has been made in the study of attention in cognitive psychological studies, single unit recordings from animals, and human and animal lesion-behavior studies. Position emission tomographic (PET) studies of local cerebral blood flow (CBF) change in the brains of normal humans will be used to address remaining questions about the identification and contribution of specific brain areas activated during the performance of tasks related to different aspects of attention. The proposed research will focus on three aspects of selective attention: 1) activation of areas related to the direction of visual spatial attention, and the relation of spatial attention to visual orienting in the form of saccadic (rapid), and smooth pursuit eye movements; 2) to identify areas that are related to attentional effects on pattern recognition through a comparison of the areas activated by the search for targets in arrays of elements that require little effort (or can take place preattentively), with areas activated when target detection in similar arrays requires exhaustive search; 3) to study the conditions necessary to activate a region (or regions) along the anterior midline that have been shown to be activated during the performance of many different tasks, and in particular to test the hypothesis that the activation of this region is concurrent with focal attention. While the main purpose of these experiments is to further our basic understanding of mechanisms underlying attention, there are clinical implications as well. There is diagnostic significance in the ability to more clearly define structure-function relationships in the brain, and the ability to determine the anatomical location, within an individual, of areas related to important functions can allow for the avoidance of these areas during neurosurgical procedures.